[FFmpeg-user] synchronisation problem on encoding video files

[Andrei Danila]

Hi,
I am writing to you guys to see if somebody can help us figure out what are we doing wrong. We are working on a project that involves users uploading video files and then we make it available to viewers in different formats. A tube website :). No matter what we try we keep getting the same problem. The result files all have a de-syncronisation of 0.3-1s between sound and video. Here is the command line that we use:

/usr/local/bin/ffmpeg -y -i input -isync -async 1 -f mp4 -threads 0 -b:v 2500k -s 1280x720 -c:v libx264 -pass 1 -preset veryslow -tune film -r 24000/1001 -an -map_metadata -1 output 
/usr/local/bin/ffmpeg -y -i input -isync -async 1 -f mp4 -threads 0 -b:v 2500k -s 1280x720 -c:v libx264 -pass 2 -preset veryslow -tune film -r 24000/1001 -c:a libfaac -b:a 128k -ar 44100 -ac 2  -map_metadata -1 output

Is it something that we are doing wrong? Is there any setting that we have overlooked? 

Thank you very much for the help!

Best regards,
Andrei Danila